Frozen product machines, such as frozen carbonated beverage (FCB) machines, utilize a freeze cylinder or freeze barrel for producing a slush beverage product. In operation of the frozen product machine, relatively warm liquid beverage product components, such as syrup and a diluent for the syrup, are delivered into the freeze barrel in a predetermined ratio. The freeze barrel is heat exchange coupled to a chilling means, such as an evaporator coil that is wrapped around the exterior of the barrel and chilled by a refrigeration system, to cool and reduce the temperature of the product mix in the barrel to below its freeze point. A beater bar and scraper assembly, powered by an electric drive motor, is within the barrel and is rotated to scrape frozen product from the inner wall of the freeze barrel and to mix it with liquid product in the barrel to form a slurry mixture of frozen beverage product for service to customers. The output torque of the motor, that is required for the motor to rotate the beater bar and scraper assembly at a nominal speed, is generally proportional to the viscosity of the product in the barrel and, therefore, to the amount of ice present in the barrel. The power draw of the motor is generally proportional to the output torque of the motor, and is sensed by a controller, usually by sensing the current or amperage draw of the motor. The controller uses the sensed power draw of the motor, which is representative of the viscosity of beverage product in the barrel and the state to which the beverage product is frozen, to operate the refrigeration system in a manner to control the consistency of product in the freeze barrel, usually by turning the refrigeration system on and off.
Drive motor systems employed to rotate beater bar and scraper assemblies in freeze barrels have upper maximum torque limits that often are not significantly greater than the torque output of the motor that is required to rotate the beater bar and scraper assembly in the preparation of relatively thick frozen beverage products. During normal operation of a frozen product dispenser, the torque output of the motor that is required to scrape ice and agitate product in a freeze barrel is below, but not significantly below, the upper torque limit of the motor. However, interim conditions can and do develop that produce torque requirements in excess of the upper limit For example, when the refrigeration system turns off, it can happen that sufficient liquid refrigerant remains in the barrel evaporator that, as it boils off, chills the barrel to a point where product in it becomes sufficiently viscous to cause an over-torque condition of the drive motor for the beater bar and scraper assembly in the barrel, in which case the output torque of the drive motor exceeds its upper limit. In typical applications, this excess torque condition is sensed by the controller, which then shuts down the drive motor and refrigeration system in order to prevent damage to the drive motor. Conventionally, this shut down of the drive motor and refrigeration requires that a service call be made to reset the frozen product dispenser error condition and correct the cause of the excess torque.
It often happens that the condition resulting in an excess torque output of the beater bar and scraper assembly drive motor is transient as can occur, for example, in response to a temporary fluctuation in the mixture of product in the barrel, which fluctuation can affect the freeze point of the product and the amount of slush ice produced in the barrel and, thereby, the torque output of the motor. Nevertheless, even though the condition causing an excess torque output of the motor is transient, the system will shut down in an error condition and a service call will be required.